Use pkg-config to determine alsa link flags. This fixes static linking.

Signed-off-by: Baruch Siach <baruch@tkos.co.il>

diff -Nuar flite-1.4-release.orig/configure.in flite-1.4-release/configure.in
--- flite-1.4-release.orig/configure.in	2009-08-14 23:46:38.000000000 +0300
+++ flite-1.4-release/configure.in	2014-04-30 18:52:33.253297236 +0300
@@ -275,7 +275,10 @@
                 #endif],
               [AUDIODRIVER="alsa"
 	       AUDIODEFS=-DCST_AUDIO_ALSA
-               AUDIOLIBS=-lasound])
+               AUDIOLIBS=`pkg-config --libs alsa`
+               if test "$shared" = false; then
+                   AUDIOLIBS=`pkg-config --libs --static alsa`
+               fi])
 AC_CHECK_HEADER(mmsystem.h,
 	      [AUDIODRIVER="wince"
 	       AUDIODEFS=-DCST_AUDIO_WINCE